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- 1 - STABILIZED LIQUID DEAMIDASE COMPOSITIONS Reference to a Sequence Listing This application contains a Sequence Listing in computer readable form, which is incorporated herein by reference. FIELD OF THE INVENTION The present invention relates to high-strength liquid deamidase compositions having improved enzymatic stability after storage. BACKGROUND Liquid enzyme compositions are popular product formats because they are easy to handle in an industrial environment. They can be pumped directly into an industrial process, and generally do not require safety measures to avoid exposure to enzyme dust, as compared to solid enzyme compositions. While solid enzyme products generally exhibit excellent enzymatic stability during and after storage, liquid enzyme products are much more challenging, because solubilized enzyme is more reactive and sensitive than enzyme on a solid form. Protein-glutamine glutaminase (“deamidase”) enzymes are protein modifying enzymes that can change proteins comprising glutamine residues. Since enzymes are also proteins, this includes self-deamidation which may modify the enzymatic activity. Higher deamidase activity increases the deamidation, and as such, liquid products with high concentrations of deamidase enzyme could be prone to reduced enzyme storage stability. It is an object of the invention to provide liquid deamidase compositions having improved enzymatic stability after storage. SUMMARY OF THE INVENTION The present invention provides, in a first aspect, a liquid enzyme composition, comprising at least 1% w/w active enzyme protein of protein-glutamine glutaminase, which has a pH in the range of pH 3.5-6. Other aspects and embodiments of the invention are apparent from the description and examples. Unless otherwise indicated, or if it is apparent from the context that something else is meant, all percentages are percentage by weight (% w/w). As used herein, the term "consists essentially of" (and grammatical variants thereof), as applied to the compositions and methods of the invention, means that the - 2 - compositions/methods may contain additional components so long as the additional components do not materially alter the composition/method. As used herein, the term "essentially free of" (and grammatical variants thereof), as applied to the compositions and methods of the invention, means that the compositions/methods may contain minor amounts of the specified component so long as the amount of the component does not materially alter, or provide any material effect on, the composition/method. In an embodiment, "essentially free of" means 0% w/w. Sequences SEQ ID NO: 1: Amino acid sequence of a deamidase from Chryseobacterium viscerum. SEQ ID NO: 2: Amino acid sequence of a deamidase propeptide from Chryseobacterium viscerum. DETAILED DESCRIPTION In the context of the invention, the term “deamidase” means a protein-glutamine glutaminase (also known as glutaminylpeptide glutaminase, or protein deamidase) activity, as described in EC 3.5.1.44, which catalyzes the hydrolysis of the gamma-amide of glutamine substituted at the carboxyl position or both the alpha-amino and carboxyl positions, e.g., L- glutaminylglycine and L-phenylalanyl-L-glutaminylglycine. Thus, deamidases can deamidate glutamine residues in proteins to glutamate residues and are also referred to as protein glutamine deamidase. Deamidases comprise a Cys-His-Asp catalytic triad (e.g., Cys-156, His- 197, and Asp-217, as shown in Hashizume et al. “Crystal structures of protein glutaminase and its pro forms converted into enzyme-substrate complex”, Journal of Biological Chemistry, vol. 286, no. 44, pp. 38691–38702) and belong to the InterPro entry IPR041325. In a preferred embodiment, the deamidases of the present invention belong to PFAM domain PF18626. Deamidases are catalytic proteins (enzymes), and the term “active (deamidase) enzyme protein” is defined herein as the amount of catalytic protein(s), which exhibits deamidase activity. This can be determined using an activity based analytical enzyme assay. This technique is well-known in the art. Deamidase activity was measured using the assay described in Example 1. The activity assay consists of two separate de-coupled parts: (1) an enzymatic step wherein ammonia is formed by the catalytic action of the protein deamidase; and (2) a non-enzymatic detection step, wherein the ammonia formed in step (1) is derivatized to a blue indophenol compound with an absorption at 630 nm. The amount of enzyme producing 1 μmol ammonia per minute at 37°C is defined as 1 unit (given in Indophenol Assay Unit: IPA(U)). The activity may be determined relative to a standard of declared streng...